Wound-wire storage battery grid and process

ABSTRACT

A storage battery grid cut from a continuous strip of wound-wire grid segments. Continuous lengths of a plurality of wires periodically are gathered into lug-forming nested loops and fanlike arrays of conductors. Nonconductive reinforcing filaments crisscross and are bonded to the conductors at a plurality of fusion-interlocked joints.

EJnited States Patent Wineadon et al. [451 Mar. 28, 1972 [54] WOUND-WIRESTORAGE BATTERY [56] References Cited GR AND ROCESS UNITED STATESPATENTS 72 I t :EllisG.Wh d 'Chl P.MCrtn 1 both of 32: as c 2,936,6705/1960 Walter ..l56/5l [73] Assignee: General Motors Corporation,Detroit, p i Examine, winston A, Douglas Assistant Examiner-C. F.Lefevour [22] Filed; Se t. 8, 1970 Attorney-William S. Pettigrew, R. J.Wallace and Lawrence B. Pl t [211 App]. No.: 70,008 an [57] ABSTRACT [51 s C 136/60 136/36 3 7 A storage battery grid cut from a continuousstrip of wound- 511 Int. Cl. ..l-l01m 35/04 wire grid segmemslengths 3581 Field of Search ..l36/60, 36,74; l56/5l,47, Periodically aregathered into lug-forming nested loops and 156/43 49 50 fanlike arraysof conductors. Nonconductive reinforcing filaments crisscross and arebonded to the conductors at a plurality of fusion-interlocked joints.

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SHEET 3 0F 4 I N VENTORS A T TORNEY WOUND-WIRE STORAGE BATTERY GRID ANDPROCESS This invention relates to grids for storage battery electrodeplates. Such grids support the plates active material and enhanceconductivity through the plates. More particularly, this inventionrelates to a wound-wire storage battery grid and a process formanufacturing a continuous strip thereof from continuous lengths ofwire. Lead-acid storage battery grids are principally commercially madeby casting the grids, usually in pairs, from appropriate lead alloys.The cast grids are then separately pasted which requires the mid-processhandling of a multitude of discrete parts. Likewise, the thusly castgrids contain more metal than is necessary to provide conductivity. Toreduce the weight and metal content of grids, it has been proposed toform a composite between a fanned current collector and a plasticsupport member. Such a composite may be found in Helms U.S. Pat. No.3,269,863 filed (8/30/66) and Wheadon et al., US. Pat. application Ser.No. 780,068, filed Nov. 29, 1968 and assigned to the assignee of thisinvention. Likewise, it has been proposed to punch grids from acontinuous strip of plastic and flame-spray the plastic to render itconductive. In this regard, see Willmann et al., U.S. Pat. applicationSer. No. 25,630, filed Apr. 6, i970 and assigned to the assignee of thisinvention. This latter approach was directed toward providinglightweight grids which could be pasted as a continuous strip ratherthan as individual grids or grid pairs. The problem has been to find theright combination of ingredients which could produce a continuous stripof grids for process ability while at the same time result in individualplates which would meet industry performance norms.

It is an object of this invention to produce continuous strips ofwound-wire battery grid segments from continuous lengths of wire andthermoplastic coated reinforcing filaments which grid segments, whenseparated from the strip, form plates meeting commercially acceptablelevels of performance. This and other objects and benefits of thisinvention will become more apparent from the detailed discussion of theprocess and drawings which follow: In this regard,

FIG. 1 is a perspective view of a portion of one embodiment of a stripof grids formed in accordance with this invention;

FIG. 2 is an end view ofthe FIG. 1 strip taken along the lines 2-2;

FIG. 3 is a plan view of an apparatus for manufacturing the grid stripof FIG. 1 in accordance with the process of this invention;

FIG. 4 is a sectioned perspective view of a grid-forming block usable inconjunction with the apparatus depicted in FIG. 3;

FIG. 5 is an enlarged, side elevation of a portion of the apparatusshown in FIG. 3;

FIG. 6, in plan view, depicts, stepwise, the grid-forming sequence ofthe blocks of FIG. 4 as they rotate through the apparatus of FIG. 3 toperform the process of this invention;

FIG. 7 is a perspective view of another grid-forming block embodimentused with the apparatus of FIG. 8;

FIG. 8 is a partial plan view of another embodiment of an apparatus formanufacturing grid strips in accordance with the process of thisinvention; and

FIG. 9 is a plan view of one embodiment of a finished grid segment cutfrom a strip prepared according to this invention.

With reference to FIGS. 1 and 2, a two-grid segment portion of a gridstrip 2 is shown. This embodiment of grid strip 2 has a plurality ofwound metal wires 4 fusion-bonded at joints 14 to reinforcing,nonconductive filaments 8. In this embodiment, a number of the filaments8a lie on one side and a number of filaments 812 on the other side ofthe wires 4. The reinforcing filaments 8 have a thermoplastic coating 12thereon. Periodically, during processing, the wires 4 are gathered toone side of the strip to form a cluster of nested wire loops 6 whichserve as conductive lugs for joining the grids to like grids in acompleted cell.

With reference to FIGS. 3 and 4, one embodiment of a process isdescribed for making the grid strip of FIGS. 1 and 2. A carrousel-likemachine 15 has an oval track 16 about an island 17. The track 16 isfilled with a number of grid-forming blocks 18 which continuouslycirculate around it. The blocks 18 (FIG. 4) have an upper working facewhere the wires 4 and filaments 8 are manipulated in a winding andgathering fashion to form a predetermined grid pattern. A plurality ofdepressible pilot pins 22 are biased upwardly through the face of block18 by springs 20. A gathering pin 24 is affixed to a slide 26 whichtogether traverse the length of the block 18 in the track 28 and betweenthe pilot pins 22 in the manner indicated. The direction of motion ofthe gathering pin is controlled by appropriate cams, not shown, locatedin the block 18 and track 16. A pair of cam-actuated jaws 30 providemeans for grasping and crimping the looped wires 6 during thelug-forming steps. The jaws rotate about the pivots 32 in response tocamming actions against the pins 33. Undercut fingers 34 at theextremities of the jaws 30 grip and crimp the loops 6 without causingthe wires at the neck 7 of the loop 6 to stack up. The individual gridsegments are formed on these blocks 18 as they progress along one leg ofthe oval with the remainder of the track 16 being utilized to return theblocks 18 to the starting position (START) of the process. At thestarting position (START), the forming blocks 18 enter closely under aplate 35 and receive a first row of filaments 8a which are payed outfrom spools 10. The plate 35 keeps the filaments and wires in place. Asthey move along the track, the blocks 18 subsequently receive rows ofwires 4 from the spools 4s and finally more filaments 8b from spools 11.Between the laying of each successive row of filaments 8 or wires 4 andbetween each series of spools, operations are performed by the blocks 18which cause gathering of the wires 4 into the desired shape. The wiresand filaments are arranged to overlie and crisscross one another priorto entering the oven 36. The precise details of these operations will bedescribed hereafter in conjunction with a discussion of the winding andgathering sequence (A-J) depicted in FIGS. 5 and 6. The strip moves intothe oven 36 where the metal wires 4 are heated and the thermoplasticcoating 12 on the filaments 8 softened. Hot and soft, the respectivewires 4 and coated filaments emerge from the oven 36 and pass beneath apress 38 which forces the hot wires into the soft plastic and unitesthem. A continuous strip of grids emanating from the press 38 passes upand over roller 48 and after trimming is ready for pasting. Since theother battery plate making steps are not a part of this invention, thestrip is depicted as being accumulated on takeup reel 50. It isunderstood, however, that uninterrupted continuous pasting, curing, etc.of a continuous strip of grids is one of the benefits of this invention.To get the process under way the ends of the wires and filaments arefixed to the lead block which begins pulling out lengths of thematerial. After this is done the wires and filaments pay outcontinuously. FIGS. 5 and 6 graphically depict the stages A-J throughwhich the processing blocks 18 pass between the points marked (START)and (FINISH) on FIG. 3 as well as the relationship between the wires 4,filaments 8, pilot 22 and gathering pins 24 at each stage. At stage A,an empty block 18 enters closely under plastic plate 35 such that thepilot pins 22 all but touch the bottom of the plate 35. At stage B,filaments 8a feed from the spools 10 onto the moving blocks 18 andbetween the pilot pins 22, as best shown in FIG. 6. At this point, thegathering pin 24 and slide 26 are in a forward position near the top ofthe block 18. As the block 18 advances from stage B to stage C cammingmeans (not shown) drive the slide 26 and gathering pin 24 downwardly inthe track 28 with the pin 24 gathering all the filaments 3a in its pathto the bottom of the block 18 (stage C). With the filaments 8a gatheredabout the pin 24 at the bottom of the block 18, a first row of metalwires 4 are laid between the upper set of pilot pins 22, as shown atstage D. As the block 18 advances between stages D and E another cammingmeans (not shown) drives the slide 26 and gathering pin 24 upwardly toagain traverse the block through the track 28 and in so doing return thefilaments 8a to their original position across the block and at the sametime gather the metal wires 4 to the top of the block 18. At the top ofthe block 18, the wires 4 are partially gripped by the fingers 34 of thejaws 30. In this regard see stage E. Unlike the filaments 8a the wires4, after being bent around the gathering and guide pins, tend to retainthe bends formed in them. As the block 18 advances between stages E andF another camming means drives the slide 26 and gathering pin 24downwardly toward the bottom of the block 18, again gathering thefilaments 8a in its path to the bottom (stage P) while leaving the wires4 loosely gripped within the jaws 30 as in stage E. With the filaments8a gathered at the bottom of the block 18, a second, but lower, row ofwires 4 are laid between the remaining pilot pins as best shown in stageG. As the block 18 advances between stages G and H the slide 26 andgathering pin 24 is again cammed upwardly through the track 28 againreturning the filaments 8a to their original position while this timegathering the lower row of wires 4 toward the upper end of the block 18(see stage H), and between the jaws 30 where they are loosely gripped asin stage 12. At stage I a second layer of filaments 8b is laid atop thewound wires 4. After the filaments 8 have been laid and the wires 4wound in the manner indicated, a camming means t stage .I completelycloses the jaws 30 thereby tightly crimping the wires together to fullyloop the wires around the gathering pin 24 and form a neck 7 between thenested loops which form the lug 6 and the fanlike array of wound wires 4diverging from the lug 6 throughout the grid segment.

After winding the grid segments in the manner indicated and with thepilot and gathering pin still extending upwardly, the forming blocks 18pass beneath a heating means, such as an infrared oven 36. The oven 36heats the thermoplastic coating on the filaments a and heats the wires 4preparatory to fusion-bonding one to the other. After leaving the oven36, block 18 passes beneath a press 38 in which the heated wires 4 andfilaments 8 are pressed together causing the wires 4 to embed in thethermoplastic coating 12 on the filaments 8 and form the fusion-bondedjoints 14. One embodiment of press 38 is shown in FIG. and involved astainless steel belt 40 which revolves at the same linear velocity asthe grid strip 2. The stainless steel belt 40 passes over rollers 44,beneath anvil 42 and is spaced from the top working face of the block 18by a distance equal to the design thickness of the grid. As the blocks18 pass beneath the anvil 42, which has a flat bottom 46, the pilot 22and gathering pins 24 are depressed into the block and against thesprings and the belt 40 applies direct pressure on the filaments 8 andwires 4 causing the wire 4 to embed in the soft thermoplastic coating12.

After the fusion-bonded joints 14 are formed in the press 38, the gridstrip 2 is ready for subsequent processing into finished battery plates.Subsequent processing steps would'include such steps as trimming thegrid strip 2 to a design width, continuously pasting the strip 2, dryingand curing the paste where necessary. However, since these latterplate-forming steps do not constitute an essential part of thisgrid-forming invention, the strip 2 is simply shown as passing over aguideroller 48 and onto a takeup drum 50. The loaded drum 50 may bestored, moved to another location in a plant for unwinding or eveneliminated as indicated above.

FIGS. 7 and 8 show another embodiment of grid-forming block 57 andstrip-forming machine 51 for carrying out the process of this inventionin the manufacture of the grid shown in FIG. 9, also part of thisinvention. With reference to FIG. 8, a portion of another carrousel-likemachine 51, with an oval track 52 and center island 53 is shown. Anumber of gridforming blocks 57 circulate around the track 52. In thismachine 51 the forming blocks 57 move through the curve 68 separatelyand move contiguously only through the straightaway portions 66 of thetrack 52. Though not shown, the curve 68 of the track 52 has a coverplate, much like the plate 35 of FIGS. 3 and 5, under which the blocks57 pass. The fixed pilot pins .58 on the forming block 57 are spacedimmediately adjacent the bottom of the plate when moving through thecurve to prevent any of the wires 54 from slipping off over theappropriate pilot pins when passing under the plate. In the embodimentof the apparatus shown in FIG. 8 the wire winding and gathering isaccomplished quite simply and with fewer moving parts than with the FIG.3 apparatus. In this embodiment, wires 54 are fed from spools 56 ontothe forming blocks 57 before the blocks 57 enter the curve 68. In orderto avoid complicating FIG. 8 by needlessly showing all the wires 54,there is shown only the outermost wire 54a and the innermost wire 54b.It is to be understood, however, that other wires from each of thespools 56 would be fed onto the blocks 57 between the several pilot pins58 and all wound and gathered together in a single operation. Thegrid-forming blocks 57 themselves have a number of fixed pilot pins 58,a depressible gathering pin 60, and a gathering pin depressing meanssuch as the button 62 which when cammed downwardly depresses thegathering pin 60 into the face of the block 57, there being anappropriate linkage (not shown) therebetween. Two of the pins 64, inaddition to being pilot pins, also serve to crimp the looped wires aboutthe gathering pin 60 during the lug formation stage. Referring again toFIG. 8, the blocks 57 with the wires 54 thereover are pulled away fromthe line of blocks in the upper straightaway 66 and one by one pulledaround the curve 68 and aligned with the blocks in the lowerstraightaway of the oval track 52. As the individual blocks 57 enter thecurve 68, a cam on the cover plate (not shown) depresses the button 62thereby depressing the gathering pin 60 below the face of the block 57.As the block 57 moves through the curve 68 with the gathering pin 60depressed, all the wires 54 bunch up near the apogee 70 of the island 53in the center of the track 52. There is one point during the path of theblock 57 through the curve 68 when the wires 54 all bunch up or collectin a very narrow region near the upper left-hand comer of the block 57between the depressed gathering pin 60 and the left lug-forming andcrimping pilot pin 64. At this point the button 62 is released. causingthe gathering pin 60 to rise and project upwardly from the face of theblock 57 thereby trapping the collected wires between the gathering pin60 and the lug-forming pin 64. The precise point in the curve 68 whereall the wires are collected as indicated will of course vary dependingon the dimensions of a given track 52 and block 57. In one particularembodiment of this type of apparatus, the forming plate 57 has a widthof about 5.5 inches, a height of about 10.6 inches and pilot andgathering pins about 0.045 inch high. The pins are spaced about 0.005inch from the bottom of the plate over the curve 68. The track 52 isabout 23.4 inches wide overall with an inner island of about 1.87 inchwide. In that embodiment the curve 68 at the end of the track 52 is moresemielliptical than semicircular and has a major axis which isperpendicular to the straightaways 66 and has an inside radius alongthat axis of about 1.38 inch and an outside radius of about 11.62inches. The minor axis of the curve which parallels the straightaways 66passes through the apogee of the island 53, has an inside radius ofabout 1.0 inch and an outside radius of about 11.35 inch. In thisembodiment the gathering pin 60 rises when the centerline of the block57 moving through the curve 68 is at about 8:30 oclock when viewing themachine from above as is done in FIG. 8. In any event, with thegathering pin 60 up and the wires 54 trapped between it and the leftlug-forming pin 64 the block 56 enters the straightaway 66 and isjostled into contiguous relation with the next preceding block 57.Alignment of the blocks 57 is facilitated by providing complementaryshaped blocks which provide an aligning camming action as the blocksenter the lower straightaway 66. During this alignment in the lowerstraightaway 66 the right-hand lug-forming pin 64 completes the loopingaction of the wires 54 around the pin 60 and slightly crimps the loopedwires to form a neck 74 in the lug 72. After the wires 54 have beenlooped and crimped about the gathering pin 60, the blocks 57 traversethe lower straightaway 66 of the track 52 where the reinforcingfilaments are applied. In this embodiment, only one layer of filaments76 is applied and that only on the top of the wound wires 54. Thefilaments 76 feed from the spools 78 located from atop the track 52, asshown. After laying the filaments 76 the strip is heated and pressed tobond the filaments and wires in much the same manner as discussed inconjunction with FIG. 3. In this embodiment, however, since the pilotpins 58 do not depress into the block 57 the press 38 must complementthe shape of the block 57 at least to the extent of having holescorresponding to the location of the pins 58. This is convenientlyaccomplished in practice by having a plurality of complementary shapedplatens (not shown) moving on a belt over the track 52 and engaging eachblock 57 at the pressing or bonding stage 38. The holes in the platensmate with the pins on the block so that the pressure is applied directlyto the wires and filaments. Other means for pressing the wires andfilaments together after heating and which are known to those skilled inthe art of machine design could also obviously be used. It is likewisenoted at this point that the straightaway portions 66 have been referredto as upper and lower. These terms have been used to simplifydescription and relate only to the orientation of FIG. 8 on thedrawings. In part, the track 52 is horizontal and therefore would nothave an upper and lower portion.

FIG. 9 shows a grid formed from the process depicted in H6. 8 after thebottom edge has been trimmed (see phantom lines). The lug 72 is a seriesof wire loops nested within each other and formed by wrapping wires 54around the gathering pin 60. A finished battery plate would have thecurved portion of the loop trimmed off (see phantom lines), asnecessary, to insure lug and plate size uniformity for subsequentprocessing. Thermoplastic coated filaments 75, 76 and 77 are attached tothe wires 54 at the fusion-bonded joints 80. In a preferred embodiment,the thermoplastic coated filaments 75 and 77, which form the upper andlower borders of the grid, comprise an extra-strong ribbon formed fromtwo spaced filaments within a single thermoplastic coating.

It is to be appreciated that the principles involved here are applicableto the manufacture of battery grids for most any electrochemical systememploying grids realizing, of course, that the selection of materialswould vary depending on the cell's reactants and environment, i.e., acidor caustic. In one particular example of this invention as it relates tothe Pb-acid battery system the metal wires are 0.045 inch diameterPballoy wire containing about 0.0015 percent Sb max, about 0.00l5percent As max, 0.05 percent Bi max, 0.08 Ca and the balance Pb. Thesewires are knurled prior to winding and looping to provide a betterfusion-bonded joint with the thermoplastic coated filaments. Thefilaments are preferably made of fiberglass strands about 0.007 inch to0.009 inch in diameter and coated with a thermoplastic material toprovide an overall diameter about 0.037 inch to 0.043 inch beforebonding. The two-filament ribbon borders are about 0.120 inch wide andabout 0.052 inch thick. The thermoplastic coating is of the hot melttype having a polyethylene base. In general though for Pb-acid batteriesa number of base polymers could be used as long as they are free frommetallics, alcohol or acetic acid and their derivatives or other batterycontaminants. A presently preferred material is known as Easto-bondM-32. The oven 30 is maintained at a temperature of about 220 F. and thewires and filaments pressed together under a pressure of about 15 psi.

While this invention has been disclosed primarily in terms of certainspecific embodiments thereof, it is not intended that it be limitedthereto, except to the extent hereinafter provided.

We claim:

1. A process for making a continuous strip of storage battery plategrids from continuous lengths of a plurality of metal grid-forming wiresand a plurality of thermoplastic coated reinforcing filaments comprisingthe steps of: progressively moving a plurality of grid-forming blocksthrough a series of processing stages, each of which blocks includes agrid-forming face, a plurality of pilot pins on said face for windingand guiding said wires over said face to form a predetermined metal wirepattern and a gathering pin for gathering said wires into a loopedcluster to one side of said block to form a grid lug; feeding said wiresonto the grid-forming face and between the pilot pins of said movingblocks; gathering said wires around said gathering pm and winding saldwires around said pilot pins to form said lug and a fan-like array ofwire fingers diverging from said lug across said face; feeding saidfilaments onto said array to form a crisscross pattern of wire fingersand filaments; heating said wires and said thermoplastic coatedfilaments; and pressing said wires and said filaments together to embedsaid wires into said thermoplastic coating and bond said wires to saidfilaments at the loci of intersection of said wires and said filaments.

1. A process for making a continuous strip of storage battery plategrids from continuous lengths of a plurality of metal gridforming wiresand a plurality of thermoplastic coated reinforcing filaments comprisingthe steps of: progressively moving a plurality of grid-forming blocksthrough a series of processing stages, each of which blocks includes agrid-forming face, a plurality of pilot pins on said face for windingand guiding said wires over said face to form a predetermined metal wirepattern and a gathering pin for gathering said wires into a loopedcluster to one side of said block to form a grid lug; feeding said wiresonto the grid-forming face and between the pilot pins of said movingblocks; gathering said wires around said gathering pin and winding saidwires around said pilot pins to form said lug and a fan-like array ofwire fingers diverging from said lug across said face; feeding saidfilaments onto said array to form a crisscross pattern of wire fingersand filaments; heating said wires and said thermoplastic coatedfilaments; and pressing said wires and said filaments together to embedsaid wires into said thermoplastic coating and bond said wires to saidfilaments at the loci of intersection of said wires and said filaments.